Bentley would only say that the announcement was made through a Liberal party press release, and couldn't clear up whether it was the party or Premier Dalton McGuinty who ultimately made the call.
He was only appointed energy minister after the election, he told a legislative committee.
"I wasn't part of that decision," he said.
"I can't answer that. I wasn't there, I wasn't part of it."
Bentley's comments came a day after he revealed the price of relocating the 300-megawatt plant to an existing coal-fired station near Sarnia. But the minister couldn't say whether taxpayers are on the hook for the move or if the cost will show up on hydro bills.
The province is facing a $15-billion deficit this year and isn't expected to emerge from the red ink until 2017.
Both opposition parties have accused the Liberals of scrapping the Mississauga plant — and another in Oakville in 2010 — in a cynical move to save seats amid fierce protest by local residents.
Taxpayers deserve to know who made the decision, whether it was the Liberal campaign director or the premier, said NDP energy critic Peter Tabuns.
"Frankly, we've been stuck with a $180-million bill and we should now who is responsible for doing that," he said.
"People will be paying more for their electricity so that the Liberals could save a number of seats in the last election."
Bentley insisted that the government only had a change of heart after listening to the strong objections of local residents.
He also pointed out that both opposition parties also promised to scrap the plant during the election and wouldn't have been able to get a cheaper deal.
Tory Leader Tim Hudak, who vowed to get rid of the plant the day before the election, said it should not have been built in the first place.
But he couldn't say whether the Tories could have struck a better deal if they'd won the Oct. 6 election.
"You can't accuse me of holding the shovel that dug that hole in the first place," he said.
"That was their decision, that was the wrong decision and now taxpayers are on the hook as a consequence."
The opposition parties want Bentley to produce certain documents about the deal, as well as those related to the cancellation of a proposed gas plant in Oakville in 2010. The minister has rejected the demand, citing solicitor-client privilege.
The committee agreed to take the matter to Speaker Dave Levac once the legislative session resumes in the fall.
Tabuns said he believes the documents will show that the Liberal party made the call because they believed they would lose several seats west of Toronto, not because they'd analyzed the area's power needs or the impact of the plant on the surrounding communities.
It's true both governments and political parties can make promises during election campaigns, he said.
"What's broken here is that cancelling a plant in the middle of an election, incurring a $180 million cost for a seat-saver is indefensible," he said.
"It may be legal, but it's certainly distasteful and wrong — epically wrong."
In 2008, the Liberals ruled out another site in Mississauga — the former coal-fired Lakeview Generating Station — as a potential site for a natural gas plant.
The government has maintained for years that new sources of power were needed in the rapidly growing communities in the southwestern Greater Toronto Area, such as Mississauga and Oakville.
Bentley said the province will be able to meet those power needs even though the new plant will be located about 260 kilometres away.
The Conservatives say the final cost will actually be much higher than Bentley claims, because a brand new plant will have to be built at the new location in a Tory riding.
Under its 20-year agreement with the province, Greenfield South Power will be paid $12,400 per month for each megawatt it supplies, said a spokeswoman for Bentley.